If you buy the blu-ray on amazon it is the blu-ray, dvd, digital copy combo pack. That's what I did to get it digitally.

https://www.amazon.com/Kubo-Two-Strings-Blu-ray-DVD/dp/B01L0YLR9W/ref=sr_1_2?crid=JXXV9IV94D4V&keywords=kubo+and+the+two+strings&qid=1571226049&sprefix=kubo%2Caps%2C187&sr=8-2